Aspirating hypodermic syringe

ABSTRACT

A hypodermic syringe for injection of anaesthetics must be designed in such a manner that aspiration can be made easily and preferably without the necessity to inject some of the anaesthetic prior to the aspiration. In syringes of the type intended for cooperation with a cylindrical ampoule having a displaceable plunger for closing one of its ends whereas the other end is closed by a diaphragm, it is further important to prevent the diaphragm and plunger from being damaged during injection so that air may enter into the ampoule. A syringe meeting these demands is provided in that a sleeve-shaped piston rod is adapted to be governed by the internal wall of the ampoule, the rod being fitted to an operating member which, however, is axially displaceable in relation to the rod and connectable directly to the plunger by means of a connecting device extending through the piston rod. The operating member is designed as a two-part plate, one part of which is shaped as a one-finger-maneuvered lever operating against projections in the piston rod and intended via the connecting device to bring about the required motion of the plunger for effecting aspiration.

ABSTRACT 5 Claims, 8 Drawing Figures Primary ExaminerRichard A. Gaudet Assistant Examiner-J. C. McGowan Attorney, Agent, or FirmHolman & Stern A hypodermic syringe for injection of anaesthetics must be designed in such a manner that aspiration can be made easily and preferably without the necessity to inject some of the anaesthetic prior to the aspiration. In syringes of the type intended for cooperation with a cylindrical ampoule having a displaceable plunger for closing one of its ends whereas the other end is closed by a diaphragm, it is further important to prevent the diaphragm and plunger from being damaged during injection so that air may enter into the ampoule. A syringe meeting these demands is provided in that a sleeve-shaped piston rod is adapted to be governed by the internal wall of the ampoule, the rod being fitted to an operating member which, however, is axially displaceable in relation to the rod and connectable directly to the plunger by means of a connecting device extending through the piston rod. The operating member is designed as a two-part plate, one part of which against projections in the piston rod and intended via the connecting device to bring about the required motion of the plunger for effecting aspiration.

. is shaped as a one-finger-maneuvered lever operating United States Patent [191 Arlers [54] ASPIRATING HYPODERMIC SYRINGE Inventor: Sven Arlers, Goteborgsvagen 77,

Partille, Sweden, 43300 Mar. 6, 1974 22 Filed:

211 Appl. No.: 448,746

[30] Foreign Application Priority Data Mar. 8, 1973 Sweden......,..................... 73032351 128/218 D, 218 C, 218 F, 219, 215, 216, 276

[56] References Cited UNITED STATES PATENTS P 8 I 2 oo 2 I 620,824 3/1949 United Kingdom............. 128/218 D US. Patfint 0a. 7,1975 Sheet 1 of3 3,910,273

'FIGJ 1 ASPIRATING HYPODERMIC SYRINGE BACKGROUND OF THE INVENTION The present invention refers to a hypodermic syringe of the type intended for cooperation with a cylindrical ampoule having a displaceable plunger which is connectable to a piston rod and intended for closing one of its ends.

The plunger of certain types of known cylindrical ampoules is designed in such a manner that it forces a diaphragm inwards, when acted upon by a piston rod, so a limited quantity of fluid is expelled. When the pressure upon the piston rod is removed the diaphragm returns to its original position, sucking fluid back into the ampoule. In this manner it is possible to ascertain if the needle has entered into a vein or in the tissue. Injection of an anaesthetic into a vein would cause grave troubles during the application of odontologic local anaesthesia. A disadvantage with syringes of known type is that it is necessary to inject some of the anaesthetic, or the like, in order to bring about the desired aspiration. During the injection it may further happen that the piston rod breaks the diaphragm, whereby air may enter the ampoule. Heavy forces upon the plunger may deform the latter, whereby the clearance between the piston and the cylinder wall will be so big that air may enter the ampoule.

A further objective is to obtain a way to better determine the quantity of fluid aspiration than has been possible with earlier types of syringes where the aspiration occurs automatically when the pressure upon the piston rod is removed.

SUMMARY OF THE INVENTION The aim of the present invention is to eliminate the disadvantages of the known syringe, and to propose a syringe of simple design, which is cheap to manufacture, handy to use and where further the aspiration and the injection may be performed without changing the grip upon the unit.

According to the invention this is brought about in that the piston rod is sleeve shaped and adapted to be governed by the cylindrical, internal wall of the ampoule, at its end remote from the ampoule said piston rod being attached to an operating member axially displaceable with respect to the piston rod, said member having a connecting device extending through the piston rod and adapted for connection to the plunger, and further being designed as a two-part plate, one part being hingedly connected to the other fixed part, the design being such that in a position where the said operating member and the said plunger are interconnected, the first mentioned part is engaging against projections at the piston rod, the said first mentioned part thereby forming an angle relative to the said fixed part.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a syringe according to the invention,

FIG. 2 is a section through the syringe according to FIG. 1,

FIG. 3 is a section perpendicularly to the section in FIG. 1,

FIG. 4 is a section similar to that of FIG. 3, but with the operating device in its inward position,

FIG. 5 shows a section similar to that of FIG. 2, but with the operating device in its aspiration position,

FIG. 6 shows a perspective view of the piston rod of the injection device,

FIG. 7 shows a perspective view of a clamping device formed as a spring, and

FIG. 8 shows a section, similar to that of FIG. 4, through a modified embodiment of the syringe.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The hypodermic syringe shown in the drawings includes a cylindrical ampoule 1, manufactured for instance of glass, one end of which being closed by a rubber diaphragm 2. This is retained at the ampoule by means of a sleeve 3, which is designed in such a manner that a fitting 4 for a needle may be snapped in place thereon, or be attached thereto in any other suitable manner.

The opposite end of the ampoule is closed by a plunger 5, preferably made of rubber and provided with a centrally located spigot 6, which extends right through the plunger and reaches a distance outside the latter, at the face thereof remote from the ampoule. The spigot 6 is connected to the plunger by means of a diaphragm, and is designed to be connected to a connecting device 7 at a piston rod 8. This is formed as a cylindrical sleeve having substantially the same external diameter as the internal diameter of the ampoule. The piston rod will thus be guided by the ampoule during the injection. The piston rod is at its back end provided with two diametrically located grooves 9 serving as guides for radially located clamping means 11, fitted internally at a cap-formed operating device 10. The clamping means 11 is designed in such a manner that it, during the axial displacement of the operating device 10 along the piston rod 8, will cooperate with the connecting device 7. This includes a U-shaped spring, between the open shanks of which the spigot 6 at plunger 5 will be gripped, when the piston rod is pushed into the cylinder ampoule. The spring 7 is mounted on a peg 12, which preferably is made integral with the spring. The ends of the peg 12, extending outside the spring, rest in diametrically located grooves 13 in the piston rod 8. During a displacement of the operating device towards the cylindrical ampoule the clamping means 11 will force the shanks of the spring 7 towards each other, and as the spigot 6 has entered into the space between the shanks the latter will grip the spigot. The clamping means 11 is designed in such a manner that it may snap into mating recesses 14 at the spring, when the plunger is connected to the spring, whereby the latter will be brought along when the operating device 10 is displaced axially.

An end plate at the operating device 10 is divided in two parts, of which a bigger one 15 is rigidly connected to the operating device 10, whereas the other part 16 is hingedly connected to the first one. When the parts 15 i and 16 are manufactured of synthetic resin the hinge connecting the parts may preferably consist of a thin bridge between the two parts. The end of piston rod 8, remote from the ampoule, is provided with two pointed projections 18 located opposite to the moveable plate part 16 and at some distance from the hinge 17. As is shown in FIG. 4 the plate part 16 will be swung outwards by means of these projections 18, when the operating device 10 is forced to its inward position, in which spring 7 is connected to the spigot 6 at the plunger. If plate part 16 is forced down it will, in cooperation with projections 18, act as a lever, whereby the operating device and the connecting device 7, as well as the spigot 6 at plunger will be lifted somewhat.

The syringe according to the invention will operate in the following manner.

A cylindrical ampoule l is connected to the piston rod unit 8, l0 and the operating device 10 thereof is forced to its inner position, whereby a plunger 5, 6 is connected to the device 7. Thereafter the needle is fitted by the fixture thereof being snapped upon the sleeve 3. Possible gas or air in the ampoule is removed in the usual manner by a small quantity of fluid being ejected from the ampoule, turned with its needle upwards. The syringe is now ready for use, and plate part 16 rests in the position shown in FIG. 4.

With all odontologic local anaesthesia it is desirable to inject the anaesthetic into the tissue, either submuscularly in the location where the anaesthesia is desired (infiltration anaesthesia) or around a nerve trunk leading to the location where it is desired to kill the pain (convection anaesthesia). Injection into a vein should be avoided from medical as well as from practical point of view, as the risks for general complications are big, and the anaesthetic will be rapidly washed away from the point of injection. It therefore is a requirement that an aspiration shall be made before the injection proper, and this is, according to the invention, brought about by forcing plate part 16 downwards, whereby spigot 6 of plunger 5 is pulled backwards sufficient to cause a sub-pressure in the ampoule. Hereby fluid from the injection locality may flow into the ampoule. If the aspiration is negative the pressure may be applied on the full plate 15, 16 whereby the piston rod will act upon plunger 5 and the injection occurs. From aspiration to injection there is no need to change the grip of the fingers around the syringe, whereby a full guarantee against intravasal injection is obtained, as the position of the needle will not be changed.

The aspiration may be repeated several times.

With the embodiment according to FIG. 8 the connection between plunger 5 and the operating device is obtained by means of a rod 19 connected to a plate 15. This rod at its end remote from the plate is formed to snap into a mating recess in plunger 5. In order to obtain the necessary centering, rod 19 is provided with an element 21. In contradistinction to the embodiment according to FIGS. l-7 the operating device according to FIG. 8 is formed to enter the piston rod 8. The operating device is provided with external keys cooperating with grooves 23 in the piston rod, whereby an angular movement of the operating device with respect to the piston rod is prevented. The invention is not limited to the embodiments shown and described, but may be varied in several ways within the scope of the claims. The cylinder ampoule may for instance be fitted into a housing, at which the needle is mounted.

What I claim is:

1. In a hypodermic syringe of the type cooperating with a cylindrical ampoule and provided with means for performing aspiration prior to injection, having a displaceable plunger connected to a piston rod and closing one end of said ampoule, said plunger being provided with an axial spigot extending from the end surface of the plunger proximate said ampoule and projecting endwise beyond the end surface of the plunger remote from the ampoule, said piston rod being sleeveshaped and telescoped within the cylindrical internal wall of the ampoule, said ampoule having a hollow needle extending from the other end thereof, the improvement wherein said piston rod at its end remote from the ampoule engages an operating device axially sliding against the outer surface of said piston rod, said operating device being connected to clamping means extending through slits in said piston rod towards the inside and engaging with said plunger over a connecting device attached to said piston rod, said connecting device extending through said piston rod and having means engaging with said axial spigot on movement of said operating device toward said ampoule, the outer end of said operating device being provided with a divided end plate, one portion of which is fixed to said operating device and the other portion being hingedly connected to said fixed portion, said hinged portion turning outwards on movement of said operating device toward said ampoule by projecting means on the outer rim of said piston rod, repositioning of said hinged portion lifting up said spigot by said connecting device, thereby causing an inward bulging of said proximate end surface of said plunger, resulting in aspiration.

2. The syringe as claimed in claim 1, in which said connecting device includes a U-shaped spring adapted to grip said spigot by way of the ends of its shanks, said spring further being adapted to cooperate with said clamping means of said operating device, said means being intended to force the shanks of the spring around the plunger when the operating device has been brought toward said ampoule.

3. The syringe as claimed in claim 2, in which the U- shaped spring is provided with recesses and the clamping means is provided with mating parts, snapping into the recesses when the operating device is brought toward said ampoule.

4. The syringe as claimed in claim 1, in which said plunger is provided with a recess and in which the connecting device includes a rod attached to the operating device, said rod, at its end remote from the operating device being provided with a head adapted to snap into the recess in said plunger. 7

5. The syringe as claimed in claim 3, in which the piston rod is provided with an axial groove, and in which the U-shaped spring is located in the piston rod by positioning means, fitting into said axial groove in the pis- 

1. In a hypodermic syringe of the type cooperating with a cylindrical ampoule and provided with means for performing aspiration prior to injection, having a displaceable plunger connected to a piston rod and closing one end of said ampoule, said plunger being provided with an axial spigot extending from the end surface of the plunger proximate said ampoule and projecting endwise beyond the end surface of the plunger remote from the ampoule, said piston rod being sleeve-shaped and telescoped within the cylindrical internal wall of the ampoule, said ampoule having a hollow needle extending from the other end thereof, the improvement wherein said piston rod at its end remote from the ampoule engages an operating device axially sliding against the outer surface of said piston rod, said operating device being connected to clamping means extending through slits in said piston rod towards the inside and engaging with said plunger over a connecting device attached to said piston rod, said connecting device extending through said piston rod and having means engaging with said axial spigot on movement of said operating device toward said ampoule, the outer end of said operating device being provided with a divided end plate, one portion of which is fixed to said operating device and the other portion being hingedly connected to said fixed portion, said hinged portion turning outwards on movement of said operating device toward said ampoule by projecting means on the outer rim of said piston rod, repositioning of said hinged portion lifting up said spigot by said connecting device, thereby causing an inward bulging of said proximate end surface of said plunger, resulting in aspiration.
 2. The syringe as claimed in claim 1, in which said connecting device includes a U-shaped spring adapted to grip said spigot by way of the ends of its shanks, said spring further being adapted to cooperate with said clamping means of said operating device, said means being intended to force the shanks of the spring around the plunger when the operating device has been brought toward said ampoule.
 3. The syringe as claimed in claim 2, in which the U-shaped spring is provided with recesses and the clamping means is provided with mating parts, snapping into the recesses when the operating device is brought toward said ampoule.
 4. The syringe as claimed in claim 1, in which said plunger is provided with a recess and in which the connecting device includes a rod attached to the operating device, said rod, at its end remote from the operating device being provided with a head adapted to snap into the recess in said plunger.
 5. The syringe as claimed in claim 3, in which the piston rod is provided with an axial groove, and in which the U-shaped spring is located in the piston rod by positioning means, fitting into said axial groove in the piston rod. 